There are 6 diatomic molecules: H2, N2, O2, Cl2, F2, Br2
Calvin (K) scale has no negative # - there is an absolute zero – no energy level
(Fo - 32)5/9 = Co
Co +273 = Ko
Graham’s Law
Rate of diffusion is inversely proportional to the square root of their molar masses
R1 = rate of diffusion of molecule A
R2 = rate of diffusion of molecule B
M1 = molar mass of A
M2 = molar mass of B
Avagadro’s Law: At STP the volume of 1 mole of any gas is 22.4L
Mass
Density = --------------Volume
Example: H2 gas
Mass – 2g
2g
D = ------------ = 0.09g
22.4L
The density of any gas is proportional to its molar mass
D2
D1
Pressure
A force applied to a certain object. One way to measure pressure is in pounds
per square inch L/in2 or g/cm2.
Pressure can also be measured in kilo-Pascals (100kPa = 5L/in2).
Pressure can be measured in atm. At sea level air pressure is approx. 1atm.
In most cases a manometer is used to measure pressure. A manometer is a Ushaped tube filled with mercury (has a very high density) when pressure is
applied the Mercury moves away (up tube) from gas. The distance between the
original end point of Hg and the endpoint after application of pressure, in
millimeters of Hg equals the amount of pressure exerted.
Open ended manometer – the pressure = deference in millimeters =
1atm
Closed ended manometers are used to measure pressure that is
significantly less that 1atm
1atm = 760 mmHg
Another way of measuring pressure is to have a basin of mercury with a vertical tube sticking out and then to
pour waster on both sides and measure how much mercury goes up tube.
KE = 1/2 mv2  kinetic energy equals half mass times velocity squared
V1
T2
velocity
V2
T1
Boyle's Law - Temperature is constant – if pressure goes up volume goes down
Charles' Law - Pressure is constant – if volume goes up temperature goes up
or
or
Gay-Lussac's Law - volume is constant – if temperature goes up pressure goes up
Combined Gas Law
or
STP  standard temperature (0o C  273o K) and pressure (1atm)
SATP  standard atmospheric temperature (25o C  298o K) and pressure (1atm)
Dalton's Law of Partial Pressures
Partial pressure of each gas is proportional to the # of moles of that gas in the mixture. Ratio of Partial P to total
P is equivalent to the ratio of the moles
Example: 3mole O2, 1 mole H2O, 1mole CO2, 0.5mole N2  5.5 mole of that gas in this gas exerts the
pressure of 1atm. How much pressure does each partial gas exert?
O2 exerts  x = 3/5.5 = 0.6atm
H2O exerts  x = 1/5.5 = 0.18atm
CO2 exerts  x = 1/5.5 = 0.18atm
N2 exerts  x = .5/5.5 = 0.9atm
101kPa = 1atm = 760mmHg
100kpa = 750mmHg
Ideal Gas Equation
(P-pressure, V-volume, n – # of moles, R – gas constant, T - temperature)
Gas constant, R
R = 0.0821 atm L / mol K if pressure is measured in atm OR
R = 8.31 kPa L / mol K if pressure is measured in mmHg
To find number of moles divide mass by molar mass  mass/molar mass =n
m
mRT
dRT
dRT
PV = --------RT

P = ---------
P = ------------ M = ------------
M
MV
M
P
Gas collected over water - Take the total pressure and subtract pressure of water at that temperature